So-called “multicharge” vehicle ignition systems have been introduced for generating multiple spark events during combustion. Multicharge ignition systems generate a succession of spark breakdowns to ensure ignition of a combustible air/fuel mixture introduced into a cylinder of an internal combustion engine. The series of sparks increases the number of ignition events and hence the probability of combustion of the air/fuel mixture by extending the time and total energy available for combustion.
In greater detail, in multicharge systems an ignition coil undergoes an initial charge (i.e., initial dwell) wherein a primary current is established in a primary winding of the ignition coil. The initial dwell is immediately followed by an initial discharge of the ignition coil wherein a secondary current in a secondary winding of the multicharge coil discharges through a spark plug to generate a first spark. Subsequent recharge intervals (i.e., subsequent dwell periods) follow, accompanied by respective discharge intervals (i.e. spark events). The number of sparks produced is generally determined by a predetermined operating strategy.
As recognized herein, it is desirable from a performance standpoint that the primary winding of the multicharge coil have low resistance so that it has concomitantly rapid charge times. This implicates the use of a relatively large diameter wire with relatively few turns. As understood herein, should the primary winding be wound with the typical even number of layers so that both ends of the wire advantageously are disposed at the low voltage side of the coil (for, e.g., ease of electrical connection), the diameter of the part would be larger than if a single layer were used, increasing both the number of primary turns and the size of the device. Thus, to both reduce overall diameter and primary coil resistance, the present invention recognizes the desirability of limiting the primary winding to only a single layer. Use of a single layer, however, presents the problem of routing one of the ends of the winding back from the high voltage end to the low voltage end, and there is limited space in current coils to effect this. With this critical recognition in mind, the solution herein is provided.